Confirmation of a gene locus for medullary cystic kidney disease (MCKD2) on chromosome 16p12

BACKGROUND: Autosomal-dominant medullary cystic kidney disease (MCKD) is an interstitial nephropathy characterized by structural renal tubular defects that result in salt wasting and a reduction in urinary concentration. The condition has clinical and morphological similarities to autosomal-recessive juvenile nephronophthisis. Two genes predisposing to MCKD have been localized. MCKD1 on chromosome 1q21 was localized in two Cypriot families, and MCKD2 on chromosome 16p12 was localized in a single Italian family. We have evaluated a large Welsh MCKD family for linkage at these two loci. METHODS: Clinical data and DNA samples were collected from affected family members. Polymorphic microsatellite markers spanning the critical regions on chromosome 1 and chromosome 16 that encompass MCKD1 and MCKD2 were analyzed. Two-point and multipoint LOD scores were calculated. RESULTS: The family fulfilled previously published criteria for the diagnosis of MCKD, but hyperuricemia and gout were not prominent features. Twenty-one affected individuals were identified. Mean age at death or end-stage renal disease was 47 years (37 to 60). Linkage and haplotype analysis generated strongly negative results at MCKD1 on chromosome 1q21 (two-point LOD score = -5.32). Strong evidence of linkage to MCKD2 was generated with a maximum multi-point LOD score of 3.75. CONCLUSION: These results provide the first independent confirmation of a gene predisposing to MCKD on chromosome 16p12 and indicate that mutation of this gene is not restricted to a single family or population. The absence of hyperuricemia and gout in our family indicates that these are not obligatory features of MCKD2 mutations.     

Differences between membranoproliferative glomerulonephritis types I and III in clinical presentation, glomerular morphology, and complement perturbation

Data for 26 patients with membranoproliferative glomerulonephritis, type I (MPGN I) and 22 with membranoproliferative glomerulonephritis, type III (MPGN III), as distinguished by glomerular ultrastructure, were analyzed to determine differences in presentation, complement perturbation, and glomerular morphology by light microscopy. MPGN III was detected with greater frequency by the chance discovery of hematuria and proteinuria in the otherwise healthy individual (MPGN III, 63%; MPGN I, 30%; P = .01) and never, in the absence of renal failure, presented with systemic symptoms such as ease of fatigue, weight loss, and pallor, as may patients with MPGN I. The more frequent detection of MPGN III by chance is evidence that its onset is insidious and that for long periods it produces no symptoms or signs. Glomerular proliferation is also less than in MPGN I. Further, in MPGN III, the complement perturbation and glomerular immunofluorescence give no evidence of classical pathway activation, for which there is abundant evidence in MPGN I. Even with severe hypocomplementemia in MPGN III, C3 nephritic factor, another cause of hypocomplementemia, is rarely detectable and then in very low concentration. The cause of the complement perturbation in MPGN III has so far escaped identification. Although these observations give evidence that MPGN III is distinct from MPGN I, there is compelling evidence from other studies that a predisposition to both types is inherited and that similar genetic factors are operative in the two types. Because their genetic basis appears to be the same, it must be concluded that despite their differences, types I and III are variants of the same disease.     

Membranoproliferative glomerulonephritis in two siblings: report and literature review

There is evidence of a genetic basis in some cases of idiopathic membranoproliferative glomerulonephritis (MPGN) types I and III, particularly those occurring in families. The clinical and morphological features and disease course in two siblings with MPGN are described. In the male sibling, both clinical and morphological features as well as serum complement profile suggested type I MPGN; electron microscopy appearance in the female sibling was consistent with type III MPGN. Both patients had treatment-resistant nephrotic syndrome which evolved into renal insufficiency in the girl. No hereditary complement deficiencies were found in siblings or their parents. Both children exhibited HLA-A24; -B27, w4; -DR11, 52; -DQ3 antigens. Between 1981 and 1996, 18 patients from eight families with unequivocal diagnosis of MPGN I or III had been described. The mode of inheritance appeared to be autosomal dominant or X-linked in four of these families. In 11 patients, including our 2, in whom HLA typing was performed, eight had the HLA-A2 antigen. Similarities and discrepancies regarding clinical and morphological features and outcomes were evident in these intrafamilial cases, suggesting either a similar genetic background or a multigenic origin of MPGN. The familial occurrence of the MPGN, highlighted by our report, supports the concept that genetically determined factors may be involved in the pathogenesis of the disease. Received: 2 September 1998 / Revised: 10 August 1999 / Accepted: 13 August 1999     

Sibling cases of nephritis resembling membranoproliferative glomerulonephritis

We have experienced rare cases of membranoproliferative glomerulonephritis (MPGN)-like nephritis, which was seen in siblings. Both the brothers had asymptomatic hematuria and proteinuria at an age before 10, 7 and 4 years old, respectively. Renal biopsy revealed proliferative glomerulonephritis, resembling MPGN type III. The family history showed that their father and grandfather suffered from end-stage renal disease, suggesting that MPGN seen in the present sibling cases is hereditary. A review of the literature revealed that familial MPGN is rare, that most of the cases have urinary abnormalities at an age of less than 10 years, and that male preponderance is seen in familial MPGN.     

Autosomal dominant medullary cystic kidney disease: evidence of gene locus heterogeneity

Autosomal dominant medullary cystic kidney disease (ADMCKD; synonym: medullary cystic disease, MCD) is an autosomal dominant kidney disorder, sharing morphological and clinical features with recessive juvenile nephronophthisis (NPH), such as reduced urinary concentration ability and multiple renal cysts at the corticomedullary junction. While in NPH end-stage renal disease (ESRD) occurs in adolescence, ADMCKD leads to ESRD in adulthood. Recently a gene locus for ADMCKD has been localized to chromosome 1q21 in two large Cypriot families. This prompted us to examine linkage in three ADMCKD-families, using the same set of polymorphic microsatellite markers spanning the critical region on chromosome 1q21. Haplotype analysis revealed that none of the three families showed linkage to this locus, thus demonstrating evidence for genetic locus heterogeneity. Additional linkage analysis studies need to be performed in order to identify further gene loci cosegregating with this autosomal dominant kidney disorder.     

Characterization of a large Lebanese family segregating IgA nephropathy.

BACKGROUND: Familial aggregation of IgA nephropathy (IgAN) suggests that genetic factors contribute to the development of this trait. Because clinical manifestations in IgAN families are often limited to episodic haematuria, large kindreds tractable to linkage analysis have been difficult to identify. METHODS: We identified a large Lebanese-Druze kindred ascertained via an index case with biopsy-documented IgAN. We performed systematic screening of 38 family members and tested linkage to reported IgAN loci. RESULTS: Screening of this family identified 16 affected individuals, including 2 individuals with biopsy-documented IgAN and 14 with chronic renal failure or abnormal urinalyses on at least three separate occasions. This kindred spanned five generations and contained five consanguineous unions. Multigenerational inheritance suggested that autosomal dominant inheritance was most likely. Phenotypic manifestations among affected individuals varied from isolated haematuria to advanced renal failure necessitating transplantation; one instance of IgAN recurrence after transplantation was also documented. Older age was associated with greater severity of disease and higher incidence of renal failure. Parametric and non-parametric analyses with 33 microsatellite markers did not reveal any evidence of linkage to reported IgAN loci on chromosomes 6q22-23, 2q36 and 4q22-31. CONCLUSIONS: We describe one of the largest multigenerational IgAN kindreds reported to date. The high incidence of renal failure among older generations suggests a significant risk of progression to renal failure. We found no evidence of linkage to known loci, suggesting that familial IgAN encompasses multiple subtypes that will require distinction based on genetic or biomarker data.     

A mechanism for the development of subepithelial deposits in a patient with type III membranoproliferative glomerulonephritis

We report on a patient with membranoproliferative glomerulonephritis (MPGN) type III, whose repeated renal biopsies show evolution from a type I-like pattern to a type III pattern of immune complex formation over a 1-year period. Based on the development of experimental in situ immune complex glomerulonephritis, we discuss possible mechanisms for the formation of subepithelial deposits in type III MPGN with reference to an experimental in situ immune complex model of glomerulonephritis.     

De novo membranoproliferative glomerulonephritis III in a renal transplant patient: case report and review of the literature

Idiopathic membranoproliferative glomerulonephritis (MPGN) is a rare cause of renal failure with a cumulative incidence of 0.3% of all ESRD and 4% of all primary glomerulonephritis for types I and II. Membranoproliferative glomerulonephritis type III is more uncommon and idiopathic de novo MPGN III in a renal transplant patient has not been reported. We present the case of a 57-year old white female patient with a diagnosis of lithium toxicity as cause of end stage renal disease (ESRD) who developed MPGN III in her allograft 6 years after a renal transplant. Despite treatment, she progressed to ESRD within four and a half years from the time of diagnosis.     

Evidence of genetic locus heterogeneity for familial bicuspid aortic valve

OBJECTIVE: We sought to determine if the gene responsible for bicuspid aortic valve (BAV) in an extended family corresponds to previously reported loci for inherited forms of the disorder. BACKGROUND: Loci at 15q25.1-26 and 9q34 have been reported to be associated with cardiovascular abnormalities involving BAV. METHODS: Linkage analysis was performed on DNA collected from a large multigenerational family in which BAV disease segregates in an autosomal dominant manner, using microsatellite markers from the regions previously reported to segregate with the phenotype. RESULTS: Lod scores were determined for genetic markers near the NOTCH1 gene and for a locus on chromosome 15q25.1-26 previously reported as being linked to BAV. The lod scores were negative or less than 1.0 for all markers tested. CONCLUSIONS: There is no evidence of linkage of BAV in our pedigree to either the NOTCH1 gene or to the chromosome 15 locus. The disorder in this family appears to be caused by a gene at a novel locus.     

家族性局灶节段性肾小球硬化一家系相关基因连锁分析

目的 对1个家族性局灶节段性肾小球硬化（FFSGS）家系的临床表型进行连锁分析,并对国内外已知的4个基因进行排除性定位。 方法 调查该家系成员的临床资料。应用两点连锁分析方法,在已知的FFSGS遗传的相关基因WT1、TRPC6、CD2AP、NPHS2所在染色体区域,选取9个微卫星遗传标记（STR）进行连锁分析。 结果 该FFSGS家系的遗传方式为常染色体显性遗传。19名家系成员中1例已进展至终末期肾病（ESRD）;4例尿检异常成员中2例病理明确诊断为FSGS;Ⅲ9和Ⅲ15患者发病年龄较早,分别为10岁和13岁;第Ⅰ和第Ⅱ代的患者均为25岁以后发病。用D1S196、D1S218、D1S238、11S935、D11S898、D11S908、D11S1986、D6S936、D6S1566等9个STR对该家系进行NPHS2、CD2AP、TRPC6和WT1基因的两点连锁分析,测得各个标记位点在重组率θ=0时,最大优势对数（LOD） 值为0.32 (D11S1986),不支持连锁。 结论 该FFSGS家系遗传方式为常染色体显性遗传。已知基因NPHS2、WT1、TRPC6、CD2AP不是该家系的致病基因。     

Renal cancer and malformations in relatives of patients with Bardet-Biedl syndrome.

BACKGROUND: Bardet-Biedl syndrome (BBS) is an autosomal recessive disorder with five loci identified thus far. The spectrum of disease includes diverse malformations of the kidney and lower urinary tract. The incidence of BBS is approximately 1/100,000 with a predicted heterozygote frequency of 1/160, and it has been suggested that heterozygotes are at increased risk of obesity and hypertension. METHODS: We describe renal disease in relatives of 109 UK BBS patients. Using PCR with fluorescent microsatellite markers we amplified DNA derived from renal tumours of affected parents to determine whether there was loss of heterozygosity at any of four BBS loci and two other gene loci associated with clear cell renal cell carcinoma (CC-RCC). RESULTS: CC-RCC was diagnosed in three of 180 BBS parents and there was loss of heterozygosity at BBS1 (11q13) in the tumour tissue of one of these subjects. In addition, there was a high incidence of renal agenesis in siblings of BBS patients and two BBS families were identified with apparently dominant inheritance of renal malformations. In one family we were able to demonstrate that renal malformations segregated with the BBS2 locus (16q21). CONCLUSIONS: Since all parents and two-thirds of siblings of BBS patients must be heterozygous for BBS mutations, our observations may implicate BBS genes in the pathogenesis of both renal cancer and malformations, both disorders of precursor cell growth and differentiation. We suggest these observations may have important implications for screening potential BBS carriers for kidney disease and may lead to a greater understanding of the aetiology of renal disease in the general population.     

Familial nephrotic syndrome: clinical spectrum and linkage to chromosome 19q13

BACKGROUND: Familial nephrotic syndrome (NS) has both autosomal dominant and recessive forms of inheritance. Recent studies in families with an autosomal dominant form of focal segmental glomerulosclerosis (FSGS) have been at odds concerning linkage to chromosome 19q13 (Mathis et al, Kidney Int 53:282-286, 1998; Winn et al, Kidney Int 55:1241-1246, 1999), suggesting genetic heterogeneity. This study examines the clinical features and confirms linkage to chromosome 19q13 in a family with autosomal dominant NS. METHODS: DNA samples were obtained from 16 of 17 family members. Genomic DNA was isolated, and polymerase chain reaction was performed for five markers spanning the area of interest on chromosome 19q13. Data were evaluated using two- and six-point linkage analysis. RESULTS: Clinical features included presentation of NS in childhood, steroid unresponsiveness, and slow progression to renal failure. Renal biopsy in affected family members showed lesions ranging from minimal change to mesangial proliferative glomerulonephritis to FSGS. Linkage was confirmed between the disease state and chromosome 19q13, with a maximum logarithm of odds (LOD) score of 2.41. Linkage was observed for a 7 cM region on chromosome 19q13, defined by markers D19S425 and D19S220. CONCLUSIONS: This study confirms the Mathis et al report of linkage to chromosome 19q13 in a family with autosomal dominant NS. However, there were notable differences in the presenting clinical and histopathologic features of our affected family members compared with those of Mathis et al. This suggests that the gene on chromosome 19q13 may be responsible for considerable phenotypic heterogeneity and variable expression in both clinical presentation and renal histopathology.     

Nephropathy associated with heroin abuse in Caucasian patients.

BACKGROUND: Renal disease is a complication of heroin addiction. Using renal biopsies in Caucasian patients, we studied the types of nephropathy associated with heroin abuse. METHODS: Nineteen renal biopsies were performed on heroin addicts between January 1993 and December 2001. The indications for renal biopsy included proteinuria with or without renal insufficiency. RESULTS: All 19 patients had serological evidence of hepatitis C virus (HCV) infection, one had hepatitis B virus surface antigen and three were HIV positive. Thirteen patients (68.4%) were found to have membranoproliferative glomerulonephritis (MPGN), 12 with type I and one with type III. Of the remaining patients, two had chronic interstitial nephritis, two had acute proliferative glomerulonephritis, one had amyloidosis and one had granulomatous glomerulonephritis with interstitial nephritis. No apparent decline in the incidence of renal disease was observed. CONCLUSIONS: In this cohort of male Caucasian heroin addicts, HCV-associated MPGN was the most frequent pattern of nephropathy, showing that the nephropathy associated with heroin abuse in Caucasians is not of the focal and segmental glomerulosclerosis type, in contrast to previous reports on African-Americans. This aspect may have important implications for patient management and prognosis.     

Membranoproliferative glomerulonephritis type I in children: correlation of clinical features with pathologic subtypes

Renal biopsies from 33 patients with membranoproliferative glomerulonephritis (MPGN) type I were reviewed to identify pathologic subtypes of this disease and assess their correlation to clinical features. The patients were divided into two groups: group A included 16 patients in chronic or end-stage renal failure and group B 17 patients with no evidence of renal insufficiency. At presentation, a nephrotic or nephritic syndrome and azotemia were equally common in both groups. The incidence of hypertension was significantly increased in group A (P less than 0.05), while recurrent gross hematuria was more common in group B. Nephrotic syndrome was more common during the course of illness in group A. Three subtypes of MPGN type I were recognized, based on whether duplication of glomerular capillary basement membranes was focal segmental (FS; 9 cases), diffuse global (DG; 18 cases), or mixed segmental and global (6 cases). Eight of nine patients showing FS MPGN type I were in group B (p less than 0.05). In contrast, 11 of 18 patients with DG MPGN type I and 4 of 6 with a segmental and global pattern were in group A (P = not significant). Therefore, FS MPGN is a good predictor of a favorable clinical outcome, whereas the other two subtypes are not. This was confirmed by a 100% actuarial kidney survival for the nine patients with FS MPGN and a 50% kidney survival of 7.5 years for patients with the other two subtypes.     

Membranoproliferative glomerulonephritis associated with low-grade B cell lymphoma presenting in the kidney

Low-grade B cell lymphoma of mucosa-associated tissue type (MALToma) rarely may involve the kidney. Membranoproliferative glomerulonephritis (MPGN) is an uncommon complication of B cell lymphoma and may be related to cryoglobulin and/or immunoglobulin synthesis by a secretory B cell clone. We report 2 patients with the novel renal biopsy findings of coexistent MALToma and MPGN. Both subjects presented with nephrotic proteinuria and renal insufficiency. One patient had a serum M protein (IgG K) but neither individual had any other clinical or serologic evidence of systemic disease, including hematolymphoid malignancy, autoimmune disease, cryoglobulinemia, or hepatitis C viral infection. Both renal biopsies demonstrated MPGN type I with immunoglobulin deposits that in 1 case showed light chain restriction (IgM K). Electron microscopy disclosed corresponding glomerular electron dense deposits in subendothelial locations. Both biopsies also contained atypical interstitial lymphoid infiltrates comprising marginal zone (centro-cyte-like) cells that infiltrated tubules and showed extra-capsular extension. Immunostains demonstrated a predominantly B cell population that lacked expression of CD5 and cycline D1, and gene rearrangement studies confirmed the presence of a monoclonal B cell population in both cases. These findings indicate that low-grade B cell lymphoma in the kidney may be an unexpected finding in patients with nephrotic syndrome related to MPGN. Immunophenotypic and gene rearrangement studies are important ancillary tools for the evaluation of atypical lymphoid infiltrates in kidney biopsies.     

Positive C1q staining associated with poor renal outcome in membranoproliferative glomerulonephritis

Background

Pathogenesis and clinical prognosis of membranoproliferative glomerulonephritis (MPGN) has not yet been established.

Methods

We conducted a retrospective study of 41 patients with MPGN (type I and III) and examined the renal survival. In addition, factors contributing to survival time were analyzed.

Results

Fourteen patients (34 %) were classified into the renal death group. Patients with nephrotic syndrome and positive C1q staining of glomerular deposits showed a particularly poor prognosis. Significantly higher frequency of nephrotic syndrome and higher urinary protein excretion were observed in the renal death group (p = 0.0002, p = 0.0002) than in the renal survival group. The intensity of C1q staining was positively correlated with the severity of the proteinuria (p = 0.004). Factors that influenced the survival time were positive C1q staining of glomerular deposits (p = 0.003), presence of nephrotic syndrome (p = 0.004), serum albumin (p = 0.02), and proteinuria (p = 0.04).

Conclusions

C1q staining in glomerular deposits and nephrotic syndrome were important factors influencing the prognosis and outcome in MPGN patients. C1q deposition may play a key role in the pathogenesis of MPGN, as evidenced by numerous observations, such as induction of proteinuria.     

Evidence for a novel type 1 diabetes susceptibility locus on chromosome 8

Type 1 diabetes results from a combination of genetic susceptibility and environmental exposures. Susceptibility loci other than HLA and the insulin gene remain to be identified to account for the degree of familial clustering observed in this disorder. Early genome-wide scans provided suggestive evidence of linkage on chromosome 8q, prompting detailed analysis of this region. A total of 20 microsatellite markers spanning an 88-cM region of 8q11-24 were genotyped in 24 type 1 diabetes pedigrees from Wisconsin that contained 39 affected sib-pairs. Multipoint linkage analyses provided close to suggestive evidence of linkage, with a multipoint logarithm of odds score (MLS) of 2.4 and Genehunter nonparametric logarithm of odds score (NPL) of 2.7 (P = 0.003). There is also evidence of linkage disequilibrium at peak marker D8S1823 for the 217bp allele (P = 0.037) using the pedigree disequilibrium test. Although our sample size was small, the multiple tests were consistent and our preliminary results suggested that 8q24 may harbor a novel population-specific type 1 diabetes susceptibility gene. Continued investigation of this region for a novel type 1 diabetes susceptibility gene appears justified.     

The pathogenesis of membranoproliferative glomerulonephritis in KwaZulu-Natal,South Africa is unrelated to hepatitis C virus infection

Idiopathic membranoproliferative glomerulonephritis (MPGN) is a well-defined clinicopathological entity with a poor prognosis, with 50% of patients progressing to end stage renal disease (ESRD) within 10 years. It was reported in about 36% of adult Black patients with nephrotic syndrome in our center previously [Seedat et al. 1988]. Hepatitis C virus (HCV) infection has been shown to be associated with cryoglobulinemic as well as non-cryoglobulinemic (or idiopathic glomerulonephritis). The aim of this study was to determine whether an association exists between HCV infection and idiopathic MPGN in a population with a relatively high prevalence of MPGN. We studied adult patients referred with glomerular disease over a two-year period, 104 patients had primary glomerulonephritis. All 23 (22%) patients with idiopathic MPGN were enrolled, as well as 32 age-matched patients presenting with other primary glomerular diseases. We examined serum from all 55 patients for evidence of HCV antibodies and HCV RNA. None of the 55 patients showed evidence of HCV infection. Chronic renal failure was present in 82.6% of the patients with idiopathic MPGN and it was advanced in 52,2%, who either were dialysis-requiring at presentation or progressed to ESRD soon thereafter; 30.4% had moderate chronic renal failure, while only 17.4% had normal renal function. HCV infection is not associated with idiopathic MPGN in our patients. Idiopathic MPGN remains an idiopathic disease, possibly with a poor prognosis in our population.